1. Field of the Invention
The present invention relates to an endoscope and, more particularly, to a color correction device for reproducing the desired colors such as natural colors of an imaged object on a display of an endoscope, and an endoscope including the color correction device.
2. Description of the Prior Art
In a clinical diagnosis using an endoscope, the color qualities of displayed images provide important guidance for distinguishing abnormal from normal parts, or for judging the severity of diseases. It is therefore crucially important for an endoscope to display the desired colors, such as the natural colors of an imaged object. In a conventional endoscope, color information is transmitted by image signals representing the tristimulus values such as R, G, B or Y, R-Y, B-Y, where a luminance Y is given, for instance, in the NTSC system by the following formula: EQU Y=0.30R+0.59G+0.11B (1)
These signals, however, are influenced by the imaging characteristics of the endoscope such as the optical properties of a scope and the electric properties of a camera unit. For this reason, it is necessary in such a conventional endoscope to perform color corrections in order to reproduce the desired colors such as natural colors of the imaged object.
Such color corrections have been performed in the conventional endoscope by operations of the color correction factors on the image signals, as represented by the following formula: ##EQU1## depending on the tristimulus values used. These color corrections have been performed conventionally under the white-balance condition, i.e., the adjustment with respect to the point representing white on the chromaticity diagram.
However, it is difficult to achieve satisfactory color reproductions by such prior art methods, because in these methods a fixed set of color correction factors is used to correct all colors regardless of their saturations or hues.